1. Technical Field
Embodiments of this disclosure relate to an image forming apparatus which periodically changes an output of a development bias to be supplied to a development unit or an output of a charging bias to be supplied to a charging unit which uniformly charges a latent-image bearing body to be rotationally driven.
2. Description of the Related Art
Image forming apparatuses are used as, for example, copiers, printers, facsimile machines, printing presses, and multi-functional devices having at least one of the foregoing capabilities. As one type of image forming apparatus, for example, an image forming apparatus disclosed in JP-H09-062042-A is known. This image forming apparatus includes a drum-shaped photoconductor serving as a latent-image bearing body and a development device provided with a development sleeve serving as a developer bearing body opposing the photoconductor at a predetermined clearance. Then, according to an electrophotographic process, a toner image is obtained by developing an electrostatic latent image formed on a surface of the rotationally driven photoconductor using a developer held on the surface of the rotationally driven development sleeve.
In this configuration, when the development sleeve has low roundness or is eccentric, a clearance (hereinafter referred to as a development gap) between the photoconductor and the development sleeve periodically fluctuates according to rotation of the development sleeve, and accordingly the strength of an electric field formed on the development gap fluctuates. Then, according to the fluctuation in the strength of this electric field, periodic image density unevenness occurs which increases/decreases an image density in the same cycle as the rotation cycle of the development sleeve.
Accordingly, the image forming apparatus disclosed in JP-H09-062042-A pre-stores a correction table for a development bias constructed based on a result obtained by inspecting a relationship between a rotation angular position of the development sleeve and a pattern of periodic image density unevenness. Then, while the rotation angular position of the development sleeve is detected, a correction amount of the development bias corresponding to the rotation angular position is specified and an output of the development bias is corrected based on a specification result. Thereby, it is possible to suppress the strength fluctuation of the electric field formed in the development gap and suppress the occurrence of periodic image density unevenness by periodically changing the development bias while following periodic fluctuation of the development gap.